1. Field of the Invention
The present invention relates to a shape measuring apparatus. For example, the present invention relates to a shape measuring apparatus which measures a shape, surface roughness, roundness, and the like of a measured object by scanning a measured object surface with or without contact. More specifically, the present invention relates to a technique which can position a detection point of the shape measuring apparatus on a user's intended measurement start point.
2. Description of Related Art
As a sensor for detecting a workpiece, there are, for example, a contact probe or stylus. Alternatively, there is known an optical or capacitance noncontact sensor and the like (JP 4929161 B and JP 2008-256679 A). In the present specification, these sensors are referred to as point sensors. These point sensors approach a measured object surface along with the normal direction of the measured object surface and detect the position (coordinates) of the measured object surface on the normal line. (It is possible to approach the surface from an oblique direction. The point sensor may approach the surface in a case that an appropriate correction function is provided.) The point sensors scan the measured object surface, and thereby a shape, surface roughness, waviness, and the like of the measured object surface on the scanning line are detected in detail. By scanning the measured object surface with the sensor, a shape measuring apparatus, which measures a shape, surface roughness, roundness, and the like of a measured object, is used.
In order to measure an object (work) with the shape measuring apparatus, first, a detection point of a point sensor needs to be set to a measurement start point. In other words, after deciding which part of the work is to be measured, the detection point of the point sensor is required to be positioned on the desired part to be measured.
As a method for positioning the detection point on the measurement start point, for example, the following method has been provided (a website publishing the applicant's products catalogue: http://www.mitutoyo.co.jp/support/service/catalog/11_gazo/14007.pdf). It is assumed that the shape measuring apparatus is equipped with an image sensor in addition to a point sensor. First, the image of the entire work is measured with the image sensor. Thus, the work image is preliminarily obtained. A range to be measured in detail in the work image is determined, and a measurement start point and a measurement end point are specified using coordinates in the work image. Then, the shape measuring apparatus moves the point sensor on the specified coordinates and starts measurement. Thus, the measurement as the user intended is performed, and the user can obtain the desired measurement result.